DIY LED Lighting for Fishtank/Aquarium Setups

I’ve got an older Marineland Eclipse 3 tank that needed a new CFL bulb (the old one was barely igniting, and the spectrum was all sorts of off). After looking into the cost for a new bulb from Mainland, I decided I would rather do a simple DIY LED upgrade than pay for the same underwhelming fluorescent bulb.

I purchased a 5M string of cool white LEDs from Amazon. They’re the 3528 size, 60 LED/meter. The important thing is that they’re the resin-coated waterproof variety. I went with the cool white for two reasons: the spectrum is better for underwater plants*, and as the resin heats and ages, it yellows slightly, making the light a bit more yellow, or warm.

I also had some of the double-sided reflective foam lying around from a previous project. Although you could do this upgrade without it, it makes for an even more light-efficient setup, as light reflected off of the water or bottom of the tank is reflected back into the tank.

The first step is to remove the previous lighting setup. The Marineland CFL bulb is held inside the hood with a few screws, so it’s easy to remove. Next, I sized out the reflective foam and glued it inside the hood using hot glue. It’s important to make cutouts for any hinged openings!

Next, I glued the LED strip in a “folded” pattern. This isn’t as clean as actually cutting the strip and taping them truly parallel, but it keeps the waterproofing intact and really reduced the amount of work needed. Soldering this waterproof strip takes a lot more work than you would think, so don’t do it unless you really need to. I used hot glue in addition to the adhesive backing on the LEDs since the adhesive isn’t super strong.

Finally (not pictured), I covered the LEDs with a few passes of packing tape and made sure everything was stuck down nicely. This isn’t required, but is a nice bit of peace of mind for when it’s all powered on. The LED strips are supposed to be waterproof, but an extra layer of protection keeping it away from the water in case the glue fails can’t hurt.

And that’s it! It looks great when it’s powered on, emits way less heat, and uses less energy than my expensive Marineland bulbs did. Not to mention that I can reduce the hours it’s on for, since the lighting is more efficient for plant growth.

*Tech-overload sidenote: Cool white LEDs are actually not emitting white light. They work by using a blue-emitting diode coated with a yellow/red coating (usually phosphorous-based) which, combined with the blue, looks white. Because of this, the spectrum of a “white” LED actually peaks highly in the blue (~450nm) with a broader peak in the red (~550-700 nm). It just so happens that the most important frequency for Chlorophyl A is right around 450nm, with a secondary peak around 700nm.